Microswitch

ABSTRACT

A microswitch with a flexible lamella is retained between individual contact lamellas which are cast in insulating material. The operating lamella is switchable by movement of an actuating lamella which in turn moves a scroll-spring to switch the operating lamella.

United States Patent Inventor Wilhelm Peter Borgmann [56] References Cited Ovemh, Germany UNITED STATES PATENTS gf 657 5 1970 3.175109 3/l965 Wodtke 200/67 1) x td if 197] 2,558,219 6/1951 K0111 ZOO/67(0) *"T" 2,5 l5,528 7/1950 Rothwell 200/67 (D) x Ass1gnee W. P. Borgmann, K.G.

Overath, Germany FOREIGN PATENTS Priority Jan,7,1969 1.077333 3/1960 Germany.... 337/343 Germany 111,422 8/1968 Denmark 337/343 G 69 00.334 Primary Examiner Bernard A Gilheany Assistant ExaminerDeWilt M. Morgan MICROSWITCH Altomey-Markva, Smith & Kruger 6 Claims, 5 Drawing Figs. M

US. Cl 200/67 D, ABSTRACT= A microswitch i h a fle i le l mell is retained 7 337/337, 337/343 between individual contact lamellas which are cast in insulatlm. Cl ..H01h 21/44, g material- Th p rating lamella is switchable by movement H01 37 52 01 37 0 of an actuating lamella which in turn moves a scrollspring to Field of Search 200/67 D, Swiwh the p r ing lam lla.

1 I4 75 5 I6 8a 2 l8 8 3 1 I 4 A 1 I I I +96 I 1: 1:: 12 6 1 12 7a i I 1 i 8c 17 7b PATENTED nnvao Ian SHEET 1 OF 3 INVENTOR W/LHELM PETEH Bonammwv PATENTED NUV30 l97l sneer 2 OF 3 INVENTOR W/u/am PE TERB RGMAN/y MICROSWITCII BACKGROUND OF THE INVENTION Microswitches are commonly used for switching in high voltage circuits. It is difiicult to achieve sufi'icient flashover stability and resistance to tracking in spite of a small construction. It is therefore an object of this invention to separate and insulate those parts carrying high an different electrical potentials so that no tracking between these parts can take place.

With known microswitches each of them having a contact plate mounted at one end thereof is for the most part encapsulated in insulating material except for the one end having the contact plate and the other end having a soldering pin. During assembly two of the contact lamellas, a flexible operating lamella and an actuating lamella are clamped together by rivets whereby the actuating lamella interpositioned between the contact lamellas; the contact point of the operating lamella being directly in line with the contact plates of the contact lamellas. A scroll-spring in the form of a bow curved about l80 extends between the actuating lamella. When operating this switch an insulated push rod is pressed against the actuating lamella which is then resiliently distorted causing the scroll-spring to be tilted in the opposite direction with respect to the operating lamella pressing the operating lamella into its operative position has accomplished.

With such microswitches it has been disadvantageous for the operating lamella to be clamped between the two contact lamellas because the flashover stability of the switch is considerably reduced. All parts carrying a potential are insulated from each other and are maintained a distance as great from each other as possible. At the same time the distance between the contact elements is critical because-by increasing the mutual distance the contact travel and therewith the switchover time is increased. The contact lamellas carry the electrical potential. Because the operating lamella is in contact with the actuating lamella, the push rod consists of insulating material or is at least insulated. Moreover only a comparatively small surface on the operating contact is available for the push rod.

PURPOSE AND SUMMARY OF THE INVENTION It is an object of the present invention to improve the known microswitches with respect to its flashover stability and to provide a switch which can be versatile and modified on the basis of a basic principle. According to the invention this object is solved by retaining the actuating lamella adjacent the outer surface of a contact lamella, whereby it projects over the contacts of the contact lamellas and by providing a scroll-spring between a bracket on the actuating lamella and the flexible operating lamella.

The operating lamella is not located between the contact lamellas but is positioned adjacent the outer surface of a contact lamella a sufiicient distance from the contact plates. This insures that there are no metal elements in the vicinity of the contact plates. so that the flashover stability of the switch is determined by the contact clearance only. The actuating lamella is connected to the operating lamella through a bracket actuating a scroll-spring and it may be selected so that its resiliency corresponds to the switching characteristics. Further it is simple to vary the resiliency of the actuating lamella by changing the clamping so that switches with different switching forces and contact travels may be produced. The individual parts do not differ from each other except for the bracing of the actuating lamella and actuating lamella itself.

Advantageously an insulating plate projecting over one of the contact lamella is located beneath the actuating lamella so that the actuating lamella does not come into close proximity to the contacts even if the push rod is pressed too far. The lamellas may be clamped together between metal plates held together by rivets. One of the metal plates located contiguous with the actuating lamella may simultaneously serve to clamp the actuating lamella and may codetermine its stiffness as it rigidly clamps part of its length.

In a special feature of the invention the actuating lamella is electrically insulated from the operating lamella by means of an insulating piece. Thus the operating lamella does not carry any electrical potential and no special construction for the operating element engaging the actuating lamella is required. Thus the actuating lamella may be made of a conducting material.

The contact lamellas conveniently have soldering pins at the ends opposite to the contacts and they are surrounded except by their ends by insulating material. With this arrangement a higher resistance to tracking is achieved because of the enlargement of the creepage path.

The microswitch according to the invention may be constructed as a bipolar switch. Thereby two pairs of contact lamellas are braced between two metal plates and the actuating elements are fastened in the middle of one of the metal plates while both the operating lamellas are connected at their end by an insulating plate which is engaged by the scrollspring from the actuating lamella. Thus the operating lamellas are rigidly connected to each other by the insulating plate and as the switching movement caused by the overturn of the scroll-spring is transfered to the insulating plate a simultaneous movement of both operating lamellas is achieved.

Further the actuating lamella may consist of a bimetal strip and the metal plate supporting said actuating lamella may extend in the direction of said lamella and may be provided with an adjusting screw for setting the rest position of the actuating lamella. When using a bimetal strip the microswitch may be used as a thermostat, e.g. on a boiler wall. If the temperature of the boiler wall reaches a predetermined value the deformation of the bimetal strip causes movement of the switch. Thus the switch may be used both as a control-and a safety element. The adjusting screw allows setting of the bias and the switch hysteresis of the actuating lamella.

The microswitch may be encapsulated in an electrically insulated airtight housing from which only the connection wires project. Such a device may be installed in damp rooms or in spaces which have an explosive atmosphere. The switch contacts may be surrounded by a nonexplosive atmosphere reducing the danger of flashovers. Because of the very small distance between the contacts it is possible to have short switchover times.

BRIEF DESCRIPTION OF DRAWINGS The invention will be described with respect to the drawings wherein:

FIG. 1 is a side view partly in section of a single-pole switch,

FIG. 2 is a view of the switch in the direction of arrow II of FIG. 1,

FIG. 3 is a plan view of a double-pole switch,

FIG. 4 is a side view of a part of said double-pole switch, and

FIG. 5 shows a further switch with a bimetal operating lamella.

DESCRIPTION OF SPECIFIC EMBODIMENTS The microswitches shown in the drawings each consist of several contact lamellas l, 2 at the ends of which are provided contact plates 12, 13. The contact lamellas l, 2 consist of flat parallel metal strips which are provided at their ends with soldering lugs for soldering to connecting wires. They have large apertures to avoid contact with the hollow rivets l4, 15 which pass therethrough and are entirely covered except at the opposite end with a plastic jackets 7, 8. An operating lamella 4 and a contact plate 3 are retained between the plastic jackets 7, 8 with the movable contact 9 lying between the contact plates l2, 13. The operating lamella 4 and contact plate 3 also have large apertures to avoid contact with the hollow rivets l4, l5 and the contact plate 3 which engages the operating lamella 4 has a soldering lug 3b.

The plastic jackets of the contact lamellas l and 2 are thinner at 7a and so that the operating lamella 4 is able to swing between both the switching positions without being impeded. At the opposite end the contact lamellas are surrounded by bases 7b, 8b of plastic to enlarge the creepage path while the soldering lug 3b directly projects from the plastic body.

The insulating element 8 includes two ring jackets 8c. one of which is shown, which are surrounding the hollow rivets l4. 15. Element 7 is provided with corresponding jackets 70, only one of which is shown. This also serves to increase resistance to tracking and centers the parts relative to each other.

On the plane flat side of the plastic element 8 an actuating lamella I6 is clamped with a metal plate 18 by means of the hollow rivets l4, 15. The opposite side of the plastic elements 7 also carries a metal plate 17. The actuating lamella 16 is separated from the contacts by a thin insulating plate and has at one end a bracket 11 which is connected to the end of the operating lamella 4 through a scroll-spring 6.

FIGS. 1 and 2 show the neutral position of the switch. Switching is caused by pressing the actuating lamella l6 downwardly as seen in FIG. 1 so that the outer end of the scrollspring 6 is squeezed over the middle axis of the operating lamella 4 driving the inner end of the scroll-spring 6, the operating lamella 4 and the movable control 9 against the contact plate 13. The switching elements tilt back into their neutral position after the operating lamella 16 has been released. lf the bracket 11 is made of nonconducting material the operating lamella 16 is insulated against all those parts of the microswitch which are electrically charged so that a push rod used to depress said operating lamella 16 could be made of conductive material.

The double-pole switch according to F IGS. 3 and 4 consists of two pairs of plastic jackets 7, 8 each of which surround contact lamellas l, 2. The two switches are connected by means of metal plates 20, only one of which is shown, located on both sides, which are kept together by rivets l4, 15. On one of the plates 20 in the middle axis of the switch a mutual operating lamella 23 is fastened by means of a further metal plate 21 and rivets 22. ln this case the actuating lamella 23 is connected to the scroll-spring 6 which leads to the rigid insulating plate 24 connecting the ends of both of the operating lamellas 4 so that the two contacts 9 are simultaneously pushed into their working position when the operating lamella 23 is depressed. In this case too the operating lamella 23 is insulated and is sufficiently spaced from those parts of the switch which are electrically charged.

It is possible in the same manner to construct a multiplepole switch having three or more units whereby mounted on a mutual insulating plate. A three-pole switch consists of threesingle-pole switches the contact lamellas of which are clamped between supporting plates together with their jackets and are parallel to each other. The operating lamellas end in the mutual insulating plate the center of which engages by the scrollspring which in turn engages the centrally clamped actuating lamella.

FIG. 5 shows a further embodiment of a switch according to the invention. This switch substantially corresponds to that of FIG. 1; the actuating lamella 29, however, consists of a strip and in place of the metal plate 18 an angle piece 26 is provided. The arm 27 of this angle piece is provided with a threaded hole in which is located a set screw 28. The end of said set screw provides the stop for the actuating lamella 29 so that the neutral position of the bimetal strip and therewith the switch hysteresis can be adjusted by rotating the set screw. The switch may be conveniently used as a thermostat by mounting it directly on a boiler wall or other heated object.

The microswitch according to the invention further may be encapsulated in an airtight housing from which only the connection wires project. The housing may be made of a suitable plastic material e.g. a strong plastic sheet, at least one wall of which should be resilient so that it is possible to press the wall against the actuating lamella from outside. Such switches may be utilized in damp rooms or in an explosive atmosphere. The switch contacts in such a design may be embedded in a nonexplosive atmosphere which also reduces danger of voltage flashovers.

lclaim: l. A microswitch comprising at least one pair of longitudinally extending contact lamellas secured at one end thereof in generally parallel relationship a fixed distance from each other, a contact member positioned at the free opposite end of each said contact lamellas, means for making an electrical connection at each of said one ends of said contact lamellas, insulating material substantially fully covering the surface of said contact lamellas extending from said contact members to the one ends thereof, a longitudinally extending operating lamella one end of which is secured between said contact lamellas and the opposite free end of which is movable into contact with said contact members alternatively, an actuating lamella secured at one end thereof adjacent said contact lamellas with the opposite free end projecting beyond the end of said contact lamellas and movable in the same direction as said operating lamella, an insulating member secured to the free end of said actuating lamella, an insulating plate between said actuating and contact lamellas, and a compression spring member positioned betwcen'said insulating member and the free end of said actuating lamella, the spring member when not compressed being longer than the distance between the insulating member and the free end of said actuating lamella whereby said operating lamella is pressed by said spring member against either of said contact lamellas at all times and movement of said actuating lamella causes said spring to be compressed over the middle axis of the operating lamella and the free end of the operating lamella to be moved from contact with one of said contact lamellas to contact with the other of said contact lamella and said insulating material, insulating plate and insulating member serve to prevent flashover.

2. A microswitch according to claim 1 wherein said compression spring member is a scroll spring.

3. A microswitch according to claim 1 wherein said contact lamellas and said operating lamella are secured together by a pair of metal plates and at least one rivet passing through said metal plates and said contact and operating lamellas located therebetween, said insulating material comprising a first insulating element surrounding the surface of one of said contact lamellas and the exterior cylindrical surface of said rivet and a second insulating element surrounding the surface of the other of said contact lamellas and a part of said first insulating element.

4. A microswitch according to claim 3 wherein one of said metal plates adjacent said actuating lamella extends towards the free end of said actuating lamella a spaced distance therefrom and includes adjusting means extending between said one plate and said actuating lamella for adjusting the rest position of said actuating lamella.

5. A microswitch as claimed in claim 1 comprising a plurality of pairs of contact lamellas and an operating lamella located between each pair and an insulating plate secured to the free ends of said operating lamellas, said compression spring member extending between said actuating lamella and said insulating plate.

6. A microswitch according to claim 1 wherein said actuating lamella comprises a bimetal strip. 

1. A microswitch comprising at least one pair of longitudinally extending contact lamellas secured at one end thereof in generally parallel relationship a fixed distance from each other, a contact member positioned at the free opposite end of each said contact lamellas, means for making an electrical connection at each of said one ends of said contact lamellas, insulating material substantially fully covering the surface of said contact lamellas extending from said contact members to the one ends thereof, a longitudinally extending operating lamella one end of which is secured between said contact lamellas and the opposite free end of which is movable into contact with said contact members alternatively, an actuating lamella secured at one end thereof adjacent said contact lamellas with the opposite free end projecting beyond the end of said contact lamellas and movable in the same direction as said operating lamella, an insulating member secured to the free end of said actuating lamella, an insulating plate between said actuating and contact lamellas, and a compression spring member positioned between said insulating member and the free end of said actuating lamella, the spring member when not compressed being longer than the distance between the insulating member and the free end of said actuating lamella whereby said operating lamella is pressed by said spring member against either of said contact lamellas at all times and movement of said actuating lamella causes said spring to be compressed over the middle axis of the operating lamella and the free end of the operating lamella to be moved from contact with one of said contact lamellas to contact with the other of said contact lamella and said insulating material, insulating plate and insulating member serve to prevent flashover.
 2. A microswitch according to claim 1 wherein said compression spring member is a scroll spring.
 3. A microswitch according to claim 1 wherein said contact lamellas and said operating lamella are secured together by a pair of metal plates and at least one rivet passing through said metal plates and said contact and operating lamellas located therebetween, said insulating material comprising a first insulating element surrounding the surface of one of said contact lamellas and the exterior cylindrical surface of said rivet and a second insulating element surrounding the surface of the other of said contact lamellas and a part of said first insulating element.
 4. A microswitch according to claim 3 wherein one of said metal plates adjacent said actuating lamella extends towards the free end of said actuating lamella a spaced distance therefrom anD includes adjusting means extending between said one plate and said actuating lamella for adjusting the rest position of said actuating lamella.
 5. A microswitch as claimed in claim 1 comprising a plurality of pairs of contact lamellas and an operating lamella located between each pair and an insulating plate secured to the free ends of said operating lamellas, said compression spring member extending between said actuating lamella and said insulating plate.
 6. A microswitch according to claim 1 wherein said actuating lamella comprises a bimetal strip. 